The museum reached a 50-year loan agreement with the U.S. Army Corps of Engineers to display the skeleton known as "Wankel T. rex."

The fossil was found in 1988 by rancher Kathy Wankel on federal land near the Fort Peck Reservoir in eastern Montana. Between 1990 and 2011, the fossil was loaned to the Museum of the Rockies in Bozeman, Mont.

The dinosaur hall is scheduled to open in 2019. Only a few museums display such nearly complete skeletons, most notably in New York City, Pittsburgh, Los Angeles and Chicago. But the Smithsonian has long wanted a T. Rex of its own for the natural history museum, which draws more than 7 million visitors each year.